Marine and aeroplane propeller



June 28, 1932. J. M. CLARK 1,864,803

MARINE AND AEROPLANE PROPELLBR Filed July 11, 1929 ATTORNEY PatentedJune 28, 1932 JOHN M. CLARK, OF WHITESTONE, NEW YORK MARINE ANDAEROPLANE PROPELLER Application filed July 11, 1929. Serial No. 377,584.

The subject of this invention has to do with the construction ofpropellers adapted to be used on aeroplanes or boats. I do not mean thatthe same propeller is used on aeroplanes and boats, but I do mean thatthe improvement in the construction of propellers, which I am about todescribe, is equally adaptable to aeroplane propellers or boatpropellers.

The object of this invention is to increase the effective area of apropeller, to give the propeller a sharper and better defined contactsurface with the fluid through which it is passing, and to prevent to avery great extent. at least propeller slip, and the foaming occasionedby the slipping of the propeller.

Another object of this invention is to direct the discharge from thepropeller blades, and by that, I mean that as the fluid leaves thepropeller blades, it is directed'into a slotted cone, and is not whippedor churned into abubbling mass, as is so often found in smoothpropellers, particularly when such propellers are operating at a highspeed.

Another object of the invention is to direct the fluid discharge towardthe outer edges of the propeller blades, as it is the outer edges, ortips of the propellers that are most eflicient. I have found thatincreased propeller efficiency is obtained when the fluid is directedtoward the blade tips, to be discharged therefrom.

The means for accomplishin these objects, and others not specifically reerred to, will be fully set forth, as the specification progresses, andthe following is what I consider the best means Qfcarrying out myinvention. The accompanying drawing should be referred to for a completeunderstanding of the specification which follows.

In the drawing:

Fig. 1 shows an aeroplane propeller in rear elevation.

Fig. 2 is a side elevation of the propeller shown in Fig. 1.

" Fig. 3 shows a marine propeller.

Fig. 4 is a sectional view taken about on the line 44 in Fig. 3.

Fig. 5 is an enlarged sectional view taken about on the line 55 of Fig.1.

Fig. 6 is an enlarged sectional view show ing modifications, and

Fig. 7 is a diagrammatic view, suggesting different shapes of groovesthat may be employed.

Similar reference numerals indicate like parts in all the figures wherethey appear.

s aeroplane propellers and marine pros pellers operate in oppositedirections, the propellers shown in Figs. 1 and 3 may be considered inreverse relation to each other. The surface of the propeller shown inFig. 1, is that surface which in operation, may be considered the backof the propeller; that is, it is the surface nearest the aircraft, andin observing this propeller, looking from before the front of anaeroplane, the surface of the propeller observed, will be flat andsmooth, as is the ordinary propeller, but the back of the propeller whenviewed in the direction above suggested, and which I term the effectivesurface of the propeller, will be provided with a plurality of grooves,and while a number of grooves may be varied, in Fig. 1, I show foursuchgrooves, as indicated by the reference characters 2, 3, 4 and 5.

It will be noted that these grooves, commencing at the hub end of eachpropeller blade, curve outward and away from the direction of rotationof the blade,

I have assumed that the direction of rotation of the propeller shown inFig. 1, is that indicated by the arrow D, and that the eneral shape ofthe grooves in the prope ler blades, as that suggested in Fig. 5.

The number of grooves, and the angle at which they are arranged, will bedetermined by the length, contour and speed of the propeller, it beingalways had in mind that it is my desire that the grooves will tend todirect the fluid outward, to be di charged at the greatest diameter ofthe propeller, or that is, fairly adjacent to the wind tips, althoughsome of the grooves, as shown at 2 and 3, are of less length than othergrooves.

I consider this also important, as I believe that were all of thegrooves to terminate at one point, a choking efiect might result.

My experiments have demonstrated that an increased propeller efl'ect isobtained by forcing the fluids outward toward the propeller tips.

In the propeller shown in Fig. 3, the same general arrangement ofgrooves is followed, but as the device shown in Fi 3, is a marinepropeller, the width of the 'b a des is greater, while the length isshorter. The greater width of blades makes it advantageous to provide agreater number of grooves.

In the propeller shown, I have provided seven grooves, indicating themwith the reference characters 6, 7, 8, 9, 10, 11 and 12,

while the propeller blades are'indicated at 13, 14 and 15. The groovesin the marine propeller are arranged in the back surface; that is,looking forward from the stern of the vessel, the grooves will be towardthe eye. This follows the general idea that the grooves are upon thepressure side, or pusher side of the blade, while the opposite side maybe smooth.

Because of the slower rotation, I believe that it is desirable to makethe grooves in the marine propeller with somewhat sharper walls, as willbe noted by observing the sectional view in Fig. 4, and comparing themwith the grooves 2 to 5 inclusive in the sectional view of Fig. 5,'whichis a sectional View through the aeroplane propeller.

In Fig. 7 I show a series of diagrams suggesting that to meet special,or other conditions, the grooves may be given a somewhat differentshape.

In Fig. 6, I show that the effect of grooves may be obtained by theaddition of a series of blocks to the surface of the propeller. Theseblocks are shown at 16, 17, 18, 19 and 20, and each is secured byscrews, or other suitable means, as shown at 21.

It is believed from the foregoing, that the operation and the results ofthe operation of my device, may be fully understood, and thatmodifications in the shape and length of grooves, or in the generalconstructive features, may be made, within the scope of the appendedclaims without departing from the principle or sacrificing theadvantages of this invention. I consider it quite important, however,that all of the grooves, or abutments, if such are used, be arranged ona true stream line, so as to reduce resistance and increase operatingefficiency.

Having carefully and fully described my invention, what I claim anddesire to secure by Letters Patent is:

1. A propeller blade having a plurality of grooves in approximately onehalf of the surface of the blade and extending longitudinally of theblade, said grooves spaced approximately equal distances apart, andterminating at one ed of the blade.

2. A propeller aving a plurality of blades, each said blade beingprovided with a plurality of grooves produced in less than the entiresurface of each blade, all of the grooves commencing at a pointapproximating the hub of a propeller and extending outward and curved toterminate at one edge of the blade in which they are produced.

JOHN M. CLARK.

